The present invention is directed towards a power generation plant and, more particularly, towards a power generation plant which converts coal gas to a useful power output.
Several recent studies have demonstrated the desirability of combining the efficiency of combined cycle power generation with coal utilization through the production of coal gas. See, for example, Sheldon et al., Economics of Power Generation from Coal Gasification for Combined Cycle Power Plants, American Power Congress, Apr. 21-23, 1975. In such systems, low BTU coal gas is generated by a coal gasifier and is converted by one or more gas turbines into a useful power output. The mechanical output of the gas turbines is typically converted into an electrical output and applied to the power grid of an electric utility.
Before the coal gas is applied to the gas turbine, undesirable constituents must be removed therefrom for both environmental reasons and to protect the integrity of the gas turbine. To this end, a cleanup system is interposed between the coal gasification plant and the gas turbines. Proper operation of the cleanup system requires that the discharge pressure of the gas leaving the cleanup system must be maintained at nearly a constant level and that rates of pressure change are also limited to an acceptable level.
The power output of the turbines must also be maintained at levels consistent with load demands. This is often difficult due to variations in the gas heating value and gas availability. Additionally, this requirement is often in conflict with the requirement that the discharge pressure of the cleanup system be maintained constant since a change in the flow of coal gas from the cleanup system to the gas turbine may result in a corresponding change in the discharge pressure of the clean-up system.